[PATCH] hw/net/vmxnet3: Fix guest-triggerable assert()

[Thomas Huth <thuth@redhat.com>]

The assert() that checks for valid MTU sizes can be triggered by
the guest (e.g. with the reproducer code from the bug ticket
https://gitlab.com/qemu-project/qemu/-/issues/517 ). Let's avoid
this problem by simply logging the error and refusing to activate
the device instead.

Fixes: d05dcd94ae ("net: vmxnet3: validate configuration values during activate")
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/net/vmxnet3.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
index 5dfacb1098..6674122a7e 100644
--- a/hw/net/vmxnet3.c
+++ b/hw/net/vmxnet3.c
@@ -1439,7 +1439,10 @@ static void vmxnet3_activate_device(VMXNET3State *s)
     vmxnet3_setup_rx_filtering(s);
     /* Cache fields from shared memory */
     s->mtu = VMXNET3_READ_DRV_SHARED32(d, s->drv_shmem, devRead.misc.mtu);
-    assert(VMXNET3_MIN_MTU <= s->mtu && s->mtu <= VMXNET3_MAX_MTU);
+    if (s->mtu < VMXNET3_MIN_MTU || s->mtu > VMXNET3_MAX_MTU) {
+        qemu_log_mask(LOG_GUEST_ERROR, "vmxnet3: Bad MTU size: %d\n", s->mtu);
+        return;
+    }
     VMW_CFPRN("MTU is %u", s->mtu);
 
     s->max_rx_frags =
-- 
2.39.3